Manufacturers and users of telecommunications equipment, networking equipment, computer systems, and other types of electronic systems comprising computing and communications functions have proposed several non-proprietary standards to reduce costs, reduce time to market, and improve performance. The dissemination and use of such non-proprietary standards, also known as open architecture standards, is believed to improve interoperability and increase reliability in products compliant with those standards. Open architecture standards for telecommunications and computing equipment may include, for example, mechanical dimensions of enclosures, racks, and electronic modules, power dissipation limits, and thermal management schemes. Open architecture standards may also include definitions of communications and control signals to be exchanged between functional elements inside a system and between the system and the outside world, electrical connector styles and pin assignments, operating voltages and currents, software commands, and data formats.
Some examples of open architecture standards for telecommunications, networking, and computer equipment include Advanced Telecommunications Computing Architecture, Advanced Mezzanine Card, and Micro Telecommunications Computing Architecture. Advanced Telecommunictions Computing Architecture, also known as ATCA and AdvancedTCA, comprises an open architecture for high-performance, high-reliability telecommunications modules. More than one AdvancedTCA module may be mechanically and electrically connected to an enclosure known in the art as a telecom shelf. A telecom shelf may have an open-frame chassis or be partially or fully enclosed. Each telecom shelf is further adapted for attachment to an equipment rack. Equipment racks having a width of 19 inches (482.6 mm) are most common, but racks with other widths are also used. More than one telecom shelf may be connected to a rack, and the rack may further be located inside a cabinet to aid in thermal management, provide electrical shielding, and provide mechanical protection. A large system may comprise more than one rack, cabinet, or a combination of racks and cabinets.
A height measurement for an AdvancedTCA module is 14.0 inches (355.6 mm), known in the art as a height of 8 U. The 8 U designation is in reference to widely recognized conventions for describing a panel height for rack-mounted equipment, wherein a height increment of 1 U corresponds to 1.75 inches (44.5 mm). The relatively large size of an AdvancedTCA module enables many complex functions to be incorporated into a single module, making AdvancedTCA an attractive solution for large, high performance systems.
One type of AdvancedTCA module is a carrier board, also known as an ATCA carrier. An ATCA carrier couples functional modules to AdvancedTCA infrastructure services such as power, ground, timing signals, data and command buses, status signals, error signals, and other input and output signals. A type of functional module designed to operate with an ATCA carrier is known as an Advanced Mezzanine Card. Advanced Mezzanine Cards, also referred to as AdvancedMCs or AMCs, comply with mechanical, electrical, power, software, and other requirements in the AdvancedTCA standard.
Up to eight AdvancedMCs may be connected to an ATCA carrier. An AdvancedMC may be connected to or disconnected from an ATCA carrier without turning off power to other modules on the carrier, a feature known in the art as hot-swapping. Hot-swapping enables maintenance to be performed on one AdvancedMC without removing other AdvancedMCs from service. AdvancedMCs help improve the overall reliability of an ATCA system because a failure in a single module will not cause the entire system to fail. Furthermore, uninterrupted system availability, a measure of system reliability, may be increased by installing as many redundant AdvancedMCs as are needed to have a desired confidence level that a preferred minimum number of AdvancedMCs is always in operation. Also, by adding or removing AdvancedMCs from a system, performance attributes such as storage capacity or rate of data transfer may be readily scaled up or down to address changes in application requirements.
While AdvancedTCA telecom shelves are well-suited for many large-scale applications, they may be too large and expensive for some applications. Another open architecture standard called Micro Telecommunications Computing Architecture, also known as MicroTCA, connects the same types of AdvancedMCs compatible with AdvancedTCA to a backplane, thereby eliminating ATCA carrier modules and enabling size and cost reductions compared to AdvancedTCA. A first version of a MicroTCA standard was released by the Compact PCI Industrial Computer Manufacturers Group (PICMG) in July 2006.
A MicroTCA system comprises at least one AdvancedMC, at least one MicroTCA Carrier Hub (MCH), and the interconnect, power, cooling, and mechanical infrastructure to support them. MicroTCA systems may vary in size from small, stand-alone enclosures comprising a small number of AdvancedMCs to installations including multiple telecom shelves with hundreds of cards. MicroTCA systems are well suited to, but are not limited to, applications requiring a smaller enclosure or applications that may operate with a lower reliability target than is generally offered by an ATCA system. Examples of MicroTCA applications include wireless Internet access points, medical instrumentation, industrial monitoring and control, digital imaging, and enterprise applications.
The MicroTCA standard recommends a height range of 2 U to 6 U (3.5 inches to 10.5 inches) (88.9 mm to 266.7 mm) for a MicroTCA telecom shelf to be mounted in a rack. Modules having a height of about 0.5 inch (14 mm) are referred to as 3 HP or alternatively as half-height. Modules having a height of about 0.7 inch (19 mm) are referred to as 4 HP or alternatively mid-size. Modules having a height of about 1.1 inch (29 mm) are referred to as 6 HP or alternatively full-size. Modules having a width of approximately 2.9 inch (74 mm) are referred to as single-width. A module with about twice the width of a single module is referred to as having double-width and one with about four times the width of a single module is referred to as having quad-width. Full-size, mid-size, and half-height modules may alternatively be made with single-width, double-width, or quad-width.
Previously, the smallest rack-mountable MicroTCA enclosure had a height of 2 U and was limited to two 6 HP AdvancedMCs. An enclosure having a height of approximately 1 U is also known in the art, but it is not rack-mountable and is limited to two 6 HP AdvancedMCs. For applications needing more than two AdvancedMCs in a rack-mountable enclosure, the solution was to use a relatively large enclosure, thereby increasing the size and cost of the finished system. Furthermore, reductions in the size of structural elements, backplanes, connectors, and other components used in enclosures having a height of 2 U or more was expected to result in rack-mountable enclosures smaller than 2 U having insufficient mechanical strength, thereby leading to reduced reliability. What is needed is a MicroTCA enclosure system that can be mounted in a 19 inch rack, holds up to ten single-width 4 HP electronic modules having a size comparable to AMCs in an enclosure having a height of 1 U, is able to operate with some electronic modules that are not fully compliant with AdvancedMC standards, and includes all necessary infrastructure for power, cooling, monitoring, and input/output, and giving adequate mechanical support to all components.